Anchorage for post-stressed concrete structures



Nov. 5, 1968 E. K. RICE 3,408,783

ANCHORAGE FOR POST-STRESS@ CONCRETE STRUCTURES Filed DeC. 28, 1967 'n Carmina-1:1.

INVENTOR. 5mm/QD /Q/ 4r @QA/EVS United States Patent O 3,408,783 ANCHORAGE FOR POST-STRESSED CON CRETE STRUCTURES Edward K. Rice, 2077 Linda Flora Drive,

Los Angeles, Calif. 90024 j Continuation-in-part of application Ser. No. 357,547, Apr. 6, 1964. This application Dec. 28, 1967, Ser. No. 697,279

2 Claims. (Cl. 52--223) ABSTRACT OF THE DISCLOSURE An anchorage intended to be embedded in a stressed concrete structure inwardly but adjacent lan end thereof, the anchorage being rigid and deninga conical wedge receiving portion intended to receive and secure a stressing tendon and surrounded by an expansion resisting plate from which extends one or more columnar elements which are bonded to the concrete to distribute to the concrete the load exerted by the anchorage.

Summary of the invention This invention relates to anchorage for post-stressed concrete structures, and is a continuation-in-part of application, Ser. No. 357,547, tiled Apr. 6, 1964, now abandoned, for Anchorage for Post-stressed Concrete Structures.

Included in the objects of this invention are:

First, to provide an anchorage which is particularly adapted for use in lightweight concrete.

Second, to provide an anchorage which incorporates an effective means of distributing or dissipating the bearing load to a relatively large volume of the concrete, thereby minimizing local crushing loads and permitting the use of lightweight, low strength concrete in stressed concrete structures.

Third, to provide an anchorage wherein rods extend axially from the anchorage into the concrete and function as columns with the load being dissipated through bond to the concrete by mechanical interlock.

Description of jigures FIGURE 1 is a fragmentary, longitudinal, sectional view of a concrete body, such as a beam or slab, showing a pair of tendons and the anchorage therefor, the tendons being shown in their unstressed condition before removal of the headers between which the concrete is cast.

FIGURE 2 is an enlarged, fragmentary, sectional View taken through 2 2 of FIGURE l with the concrete omitted, and showing one of the anchorage and adjacent portions of a tendon.

FIGURE 3 is a further enlarged, sectional view taken through 3-3 of FIGURE 2 showing an anchorage embedded in the surrounding concrete with the tendon shown in its stressed condition and sealed in place.

The concrete body or structure 1 in which the anchorage is employed may be a beam or slab cast within a suitable form which includes headers 2. Extending between the headers 2 are tendons 3. Each tendon may be a single wire, multiple wire strand, or a more complex cable.

In the casting of a concrete slab, it is customary to place a pair of tendons side by side throughout the major length of the slab and divide the tendons within the end margins of the slab, as shown in FIGURE l. If the concrete beam or slab is stressed by a post-tensioning process, the tendons 3 are placed in the form before pouring the concrete and are initially, substantially tension-free, It is customary to 3,408,783 latented Nov. 5, 1968 coat .the tendons3with a lubricant and coverwith a sleeve 4 to permit elongation of the tendons 3. after the concrete has set. l ,y

The anchorage is employed to `secure the Atendons 3 after the tendonshave beenv elongated. The anchorage `includes an anchor bodyS, preferably formed of ya helical coil .of-heavy wire, and having a cylindrical ,portion 6 and a conical portion 7.,'lhe conical portion 7 receives wedges 8 adapted to. gripthe tendons, as shown in FIGURE 3.

.by the` wedges 8 is a plate 9 dirnensioned to form a radially rigid constraining means to" prevent radial expansion of the conical portion 7 vvhensubjectedto the loads imposed by the wedges 8. The plate 9 may be brazed cemented, or otherwise bonded to the anchor body 5. It is4 preferred to use a cement or adhesive, such as an epoxy resin, to avoid heating and thus reducing the strength of the anchor body 5. The wire forming the coils of the anchor body is of large diameter and therefore quite stiff so that as used, the anchor body is, essentially, a rigid body, and forms with the permanently attached plate 9, a unitary rigid structure.

Initially, each anchor body 5 receives a longitudinally split rubber plug 10 having a conical portion 11 fitted within the conical portion 7, and an enlarged cylindrical portion 12 covering the large end of the anchor body 5. The anchor body is initially held in place by means of nails 13 inserted through holes provided in the plate 9 and adapted to be driven into the header, as shown in FIG- URE 2. The nails serve to press the anchor body against the cylindrical portion of the rubber plug 10 so as to seal that portion of the anchor body 5 which later receives the wedges S.

It is often desirable to stress beams or slabs formed of lightweight aggregate concrete. Such concrete has low strength. It is therefore essential that the loads imposed by the tendons 3 be distributed or dissipated in the concrete in such a manner as to avoid high unit loads. This is accomplished by means of symmertically placed loaddistributing rods 14 secured to the plate 9 and extending axially into the concrete body essentially parallel with the tendons 3. In the construction illustrated, two such rods are shown for each tendon.

The rods 14 are bonded to the surrounding concrete. While they are indicated as cylindrical, they may be twisted or provided with nodules in the manner of concrete reinforcing rods. The length of the rods 14 is determined by the load imposed by the tendons 3 and the strength of the concrete aggregate.

Suicient surface is provided to maintain the unit load between the rods 14 and the concrete well below the strength of the concrete. The rods 14 act essentially in the manner of steel columns and are capable of carrying large loads since they are completely supported against bending by the surrounding concrete. The rods 14 avoid local crushing loads which have in the past limited the use of bearing plates for the transmission of loads to lightweight aggregate concrete.

The plates 9 associated with the series of tendons 3 may be employed as a convenient means for locating transversely-extending, reinforcing bars 15. It should be understood, however, that such bars extending transversely to the plates 9 do not perform the function of the rods 14 in transmitting the loads from the tendons 3 to the surrounding concrete.

While a particular embodiment of this invention has been shown and described, it is not intended to limit the same to the exact details of the construction set forth, and it embraces such changes, modifications, and equivalents of the parts and their formation and arrangement as come within the purview of the appended claims.

Y(ib) a 'wedge ttingsaid, Wedge-receiyingielenient indons extending between ancjlorage zones at the ends of to distribute to the concrete the load exerted by said said structure; anchorage means in `at least one of said tendon on said anchorage means.

'zones andhavi'rig'an' end"Iier/fioriy of one of said tendons 5 2. A stressed concrete. structure, as defined in claim 1,

secured therein, saidanchorai'g'e rneans comprising: wherein:v l' i i (a) a unitaryrigid means, embedded in said concrete (a) said plate is'provided with a plurality of said rigid Y' structureinwardly from the Vadja'cii'lt end thereof; columnar elements vsymmetrically arranged about said said unitary' rigid" means including an internally i tendon. f "I i v` conical Wedge-re'ceiyingelement surrounding an end 10 Y 'i References Cited y lportion of said y tendo,'a plate surrounding and rigid- UNITED STATES PATENTS ly secured to'said element andeitendinglaterally A ,i i

` thereof, andatlastlone"elongated'rigid "columnar 618,147 11/1952 Ffeyssmet 52-223 g element rigidly fixed at oneend to a face of said FOREIGN' PATENTS platev and extending away'frm said adjacent end 15 1" f generally barallel'to fbut laterally spaced' from said 9.05347 4/1965 France' i tendon in Saidanhoragefzone;

FRANK L. ABBOTT, Primary Examiner. i. L. lRlDGlLL, kIR., Assistant Examiner.

wardly of said plate; 

